LIBC Blog

Universiteit Leiden

How to run away from your problems

The runner finds his exercise fun and relaxing, yet the body’s stress response is activated.This makes sense from an evolutionary perspective: running after your meal or running to not become one is stressful. How can it be that the runner isn't stressed?

It is well-established that, while running, the body’s stress response is activated: the hypothalamic-pituitary-adrenal (HPA) axis1. But how can it be then, that the runner isn’t constantly stressed while he has to deal with elevated levels of cortisol, the body’s main stress hormone?

This is particularly puzzling knowing that anxiety disorders and depression are characterized by stress response activation as well2.

So, what happens to the runner’s body?

As the runner goes about his business, levels of stress hormones rise, and stay elevated for at least two hours after the run. On a rest day, the runner’s cortisol levels are similar to the couch potato’s3.

There are indications that running improves health4, memory and concentration5. This is due to a chemical responsible for neuronal growth, called brain-derived neurotrophic factor (BDNF). Running boosts release of this substance in two important areas: the frontal cortex (responsible for cognitive functions) and the hippocampus (essential in memory processes)5. However, the effects of stress are exactly opposite. What’s going on?

The brain adapts

The runner has a greater amount of stress hormone inactivation overnight, and this inactivation adapts to the amount of exercise6. So, doubling the amount of running in a week doubles the amount cortisol inactivation during the nights.

In addition, the pituitary becomes less sensitive to the stress hormones3. This is like when you start using a new deodorant: at first you are very aware of the smell, but as you use it more often, you hardly notice it.

The brain is high

Forget the oft-mentioned endorphin explanation of the “runner’s high’7 . Essential to our solution are endocannabinoids—yes, the brain’s self-produced cannabis. Going for a good run apparently boosts the release of these cool chemicals, which not only make you feel pleasant, relaxed, and increase your pain tolerance, they also tell the frontal cortex to stop fussing, and so dampen the stress response8!

What’s more, depression and anxiety disorders are related to lower levels of these endocannabinoids9. Exercise benefits not only clinical populations, but also healthy people: it decreases hormonal and heart rate response to stress10.

So, how do I run away from my troubles?

There is only a relative answer: run quite far, but not too far. Similarly, run quite hard, but not too hard. Running at 70-85% of your capacity (based on maximum heart rate) boosts your brain-cannabis the most, and so reduces stress the most.